1. Field of the Invention
The present invention relates to a filter plate for presses for pressing cocoa pastes.
2. Description of Related Art
As is known, in the terminal stage of treatment of cocoa paste in the liquid state, separation is carried out of the liquid phase of cocoa butter from the solid phase in presses which have a number of reciprocally movable pistons and which bear, on the side turned towards the pressing chambers, a filter plate. Presses and filter plates of this type are known to the art.
Known filter plates accommodate, on the side turned towards the pressing chamber, a filter gauze of very fine mesh and have a plurality of through-holes opening into channels which are open on the side turned towards the associated piston. A number of concentric channels are provided, connected to a more external collecting discharge channel by means of a plurality of radial channels. It follows that the through-holes of the filter plates are likewise arranged according to concentric circumferences and radial lines. The collecting discharge channel faces with one of its sections a discharge hole for the cocoa butter made in the associated piston.
In the stage of pressing the cocoa pastes, it is important to achieve maximum anticipated extraction of the expensive cocoa butter and to carry out such extraction in the briefest possible time. In known filter plates, between the concentric channels and the radial channels of the through-holes, there is a plurality of blind annular sectors, that is to say without through-holes and of relatively large surface area.
These known filter plates have various disadvantages. Constructionally, the execution of the concentric channels and of the radial channels and of the high number of through-holes is costly. The residue of cocoa butter on the cake is distributed in zones in rather an irregular manner, which aggravates the measurement of the residual cocoa butter according to the relative standards. It is not possible to shorten the pressing times. At the end of the pressing stage, the presence of the blind circular sectors brings about in the cake the formation of pockets of deposit of cocoa butter which are difficult to evacuate. In these zones, upon the release of the oil-hydraulic pressing pressure, suction of cocoa butter is created which, from the through-holes of the filter plate, returns into the cake and thus contributes to creating on the cake zones with irregular distribution of cocoa butter. These non-uniform cakes then aggravate working in the pulverizing mill.